Validating the assumption that food calls attract groupmates

Several functional hypotheses have been proposed to explain the function of food-associated calling in primates. Food calls may provide information about a food source, serve as an offer to share food, or reduce predation risk while foraging by informing groupmates of food discovery. Common to these hypotheses is an assumption, largely untested, that animals approach when they hear a groupmate food calling. Recent evidence suggests that food calls of Cebus species elicit groupmate approach. The purpose of the present study was to test this assumption in the genus Callithrix. Two family groups (N=15) of captive-born Geoffroy’s marmosets (C. geoffroyi) were presented with playbacks of groupmate food calls, non-groupmate food calls, and a no-sound control condition. We scored subjects’ approach and the latency to the first approach in each trial. Based on a randomization test for two dependent samples, we found that subjects were significantly more likely to approach after playback of groupmates’ food calls in comparison to the no-sound control condition (p = 0.0004). A comparison of groupmate and non-groupmate food call trials suggests a selective approach response; the marmosets approached groupmate food calls more quickly than non-groupmate food calls. Our results support the plausibility of functional hypotheses, such as those listed above, that depend on the approach of groupmates in response to food calls.